Jiangsu Key Laboratory for Microbes and Functional Genomics, Jiangsu Engineering and Technology Research Centre for Microbiology, College of Life Sciences, Nanjing Normal University, Nanjing, China.
Virulence. 2021 Dec;12(1):1091-1110. doi: 10.1080/21505594.2021.1909954.
In eukaryotes, calcium not only is an essential mineral nutrient but also serves as an intracellular second messenger that is necessary for many physiological processes. Previous studies showed that the protein phosphatase-calcineurin protects fungi from toxicity caused by the extracellular calcium; however, little is known about how calcineurin mediates the cellular physiology process for this function. In this study, by monitoring intracellular calcium, particularly by tracking vacuolar calcium dynamics in living cells through a novel procedure using modified aequorin, we found that calcineurin dysfunction systematically caused abnormal intracellular calcium homeostasis in cytosol, mitochondria, and vacuole, leading to drastic autophagy, global organelle fragmentation accompanied with the increased expression of cell death-related enzymes, and cell death upon extracellular calcium stimuli. Notably, all detectable defective phenotypes seen with calcineurin mutants can be significantly suppressed by alleviating a cytosolic calcium overload or increasing vacuolar calcium storage capacity, suggesting toxicity of exogenous calcium to calcineurin mutants is tightly associated with abnormal cytosolic calcium accumulation and vacuolar calcium storage capacity deficiency. Our findings provide insights into how the original recognized antifungal drug target-calcineurin regulates intracellular calcium homeostasis for cell survival and may have important implications for antifungal therapy and clinical drug administration.
在真核生物中，钙不仅是一种必需的矿物质营养物，而且还是细胞内的第二信使，对许多生理过程都是必需的。先前的研究表明，蛋白磷酸酶钙调神经磷酸酶可保护真菌免受细胞外钙引起的毒性；然而，对于钙调神经磷酸酶如何介导该功能的细胞生理过程，人们知之甚少。在这项研究中，通过监测细胞内钙，特别是通过使用改良的水母发光蛋白通过一种新程序跟踪活细胞液泡内钙动力学，我们发现钙调神经磷酸酶功能障碍会系统性地导致细胞质、线粒体和液泡中异常的细胞内钙稳态，导致严重的自噬，伴随细胞死亡相关酶表达增加的整体细胞器碎片化，以及在细胞外钙刺激下的细胞死亡。值得注意的是，钙调神经磷酸酶突变体的所有可检测到的缺陷表型都可以通过减轻细胞质钙超载或增加液泡钙储存能力显著抑制，这表明外源钙对钙调神经磷酸酶突变体的毒性与细胞质钙积累异常和液泡钙储存能力不足密切相关。我们的研究结果为人们了解最初被认可的抗真菌药物靶标钙调神经磷酸酶如何调节细胞内钙稳态以维持细胞存活提供了新的见解，这可能对抗真菌治疗和临床药物管理具有重要意义。
